Sunflower oil is the non-volatile oil compressed from sunflower (Helianthus annuus) seeds. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient. The world's largest sunflower oil producers now are Russia, Ukraine and Argentina.
Sunflower oil is a monounsaturated (MUFA)/polyunsaturated (PUFA) mixture of mostly oleic acid (omega-9)-linoleic acid (omega-6) group of oils. The oil content of the seed ranges from 22 to 36% (average, 28%): the kernel contains 45–55% oil. The expressed oil is of light amber color with a mild and pleasant flavor; refined oil is pale yellow. Refining losses are low and the oil has good keeping qualities with light tendency for flavor reversion. The oil contains appreciable quantities of vitamin E, sterols, squalene, and other aliphatic hydrocarbons.
In recent years, there has been an increase in demand for sunflower crops such as sunflower oil. Measures such as the development of hybrid sunflowers to increase oil production have been introduced to meet this demand.
Sunflower oil is mainly a triglyceride; a typical constituent is shown. The British Pharmacopoeia lists the following profile:
- Palmitic acid (saturated): 5%
- Stearic acid (saturated): 6%
- Oleic acid (monounsaturated omega-9): 30%
- Linoleic acid (polyunsaturated omega-6): 59%
Several types of sunflower oils are produced, such as high linoleic, high oleic and mid oleic. Mid-oleic sunflower oil typically has at least 69% oleic acid. High oleic sunflower oil has at least 82% oleic acid. Variation in unsaturated fatty acids profile is strongly influenced by both genetics and climate. In the last decade, high stearic sunflower lines have been developed in Spain to avoid the use of partially hydrogenated vegetable oils in the food industry.
Sunflower oil is high in the essential vitamin E and low in saturated fat. The two most common types of sunflower oil are linoleic and high oleic. Linoleic sunflower oil is a common cooking oil that has high levels of polyunsaturated fat. It is also known for having a clean taste and low levels of trans fat. High oleic sunflower oils are classified as having monounsaturated levels of 80% and above. Newer versions of sunflower oil have been developed as a hybrid containing linoleic acid. They have monounsaturated levels lower than other oleic sunflower oils. The hybrid oil also has lower saturated fat levels than linoleic sunflower oil.
The phosphatides (0.1–0.2%) present in the oil are lecithin (38.5%) and cephalin (61.5%); they occur in combination with protein and carbohydrates. Sunflower oil also contains lecithin, tocopherols, carotenoids and waxes. Sunflower oil's properties are typical of a vegetable triglyceride oil.
Several varieties of sunflower oilseeds have been developed by standard plant breeding methods, mainly to vary the amount of oleic acid and linoleic acid which, respectively, are the predominant monounsaturated and polyunsaturated fats in sunflower oil.
While the original oilseed was high in linoleic acid, a polyunsaturated ω-6 fatty acid, a premium high oleic acid strain was developed in the late twentieth century. Early in the 21st century, a mid-oleic strain marketed as Nu-Sun was introduced as an improved frying oil that would have a low level of saturated fat, but would not require hydrogenation. These three major strains have been purposely bred to differ in their levels of monounsaturated and polyunsaturated fats, saturated fat and tocopherols. All seed hybrids and the resulting different sunflower oils are mostly devoid of essential nutrients, with the notable exception of vitamin E which is high in content in all varieties (nutrient tables).
Because sunflower oil is primarily composed of healthier-but-less-stable polyunsaturated and monounsaturated fatty acids, it can be particularly susceptible to degradation by heat, air, and light (which trigger and accelerate oxidation. Keeping sunflower oil at low temperatures during manufacture and storage can help minimize rancidity and nutrient loss—as can storage in bottles that are made of either darkly-colored glass, or, plastic that has been treated with an ultraviolet light protectant.
Sunflower oil can be extracted using chemical solvents (e.g., hexane), or expeller pressing (i.e., squeezed directly from sunflower seeds by crushing them). "Cold-pressing"/expeller-pressing sunflower seed oil under low-temperature conditions is a preferred method, for those seeking an extraction process that doesn't involve chemical solvents, as well as for people following a raw foods diet.
Refining sunflower oil through solvent extraction, de-gumming, neutralization, and bleaching can make it more stable and suitable for high-temperature cooking; but, will also remove some of the oil's nutrients; flavor; color (resulting in a pale-yellow); free fatty acids; phospholipids; polyphenols; and, phytosterols. Unrefined sunflower oil is less heat-stable (and therefore well-suited to dishes that are either raw or cooked at low temperatures); but, will retain more of its original nutrient content, flavor, and color (light-amber).